get_current_line.ts

// From https://github.com/bevry/get-current-line/tree/master (MIT-licensed)

/** The combination of location information about the line that was executing at the time */
export interface Location {
	/** the location of the line that was executing at the time */
	line: number
	/** the location of the character that was executing at the time */
	char: number
	/** the method name that was executing at the time */
	method: string
	/** the file path that was executing at the time */
	file: string
}

/**
 * If provided, continue skipping until:
 *
 * 1. The file or method is found
 * 2. Once found, will continue until neither the file nor method are found anymore
 * 3. Once exited, the frame offset will then apply
 *
 * If you wish to capture the found method or the file, combine them with `frames: -1` or `immediate: true`.
 *
 * If you wish for more customisation than this, create an issue requesting passing a custom skip handler function, as more variance to this interface is too much customisation complexity.
 */
export interface Offset {
	/**
	 * if provided, continue until a method containing or matching this string is exited
	 * if provided alongside a file, will continue until neither the file nor method are found
	 * this allows file and method to act as fallbacks for each other, such that if one is not found, it doesn't skip everything
	 */
	method?: RegExp | string | null
	/**
	 * if provided, continue until a file containing or matching this string is exited
	 * if provided alongside a method, will continue until neither the file nor method are found
	 * this allows file and method to act as fallbacks for each other, such that if one is not found, it doesn't skip everything
	 */
	file?: RegExp | string | null
	/**
	 * once we have satisfied the found condition, if any, then apply this index offset to the frames
	 * e.g. 1 would mean next frame, and -1 would mean the previous frame
	 * Use -1 to go back to the found method or file
	 */
	frames?: number
	/**
	 * once we have satisfied the found condition, should we apply the frame offset immediately, or wait until the found condition has exited
	 */
	immediate?: boolean
}

/**
 * For an error instance, return its stack frames as an array.
 */
export function getFramesFromError(error: Error): Array<string> {
	// Create an error
	let stack: Error['stack'] | null, frames: any[]

	// And attempt to retrieve it's stack
	// https://github.com/winstonjs/winston/issues/401#issuecomment-61913086
	try {
		stack = error.stack
	} catch (error1) {
		try {
			// @ts-ignore
			const previous = err.__previous__ || err.__previous
			stack = previous && previous.stack
		} catch (error2) {
			stack = null
		}
	}

	// Handle different stack formats
	if (stack) {
		if (Array.isArray(stack)) {
			frames = Array(stack)
		} else {
			frames = stack.toString().split('\n')
		}
	} else {
		frames = []
	}

	// Parse our frames
	return frames
}

const lineRegex =
	/\s+at\s(?:(?<method>.+?)\s\()?(?<file>.+?):(?<line>\d+):(?<char>\d+)\)?\s*$/

/**
 * Get the locations from a list of error stack frames.
 */
export function getLocationsFromFrames(frames: Array<string>): Array<Location> {
	// Prepare
	const locations: Array<Location> = []

	// Cycle through the lines
	for (const frame of frames) {
		// ensure each line is a string
		const line = (frame || '').toString()

		// skip empty lines
		if (line.length === 0) continue

		// Error
		// at file:///Users/balupton/Projects/active/get-current-line/asd.js:1:13
		// at ModuleJob.run (internal/modules/esm/module_job.js:140:23)
		// at async Loader.import (internal/modules/esm/loader.js:165:24)
		// at async Object.loadESM (internal/process/esm_loader.js:68:5)
		const match = line.match(lineRegex)
		if (match && match.groups) {
			locations.push({
				method: match.groups.method || '',
				file: match.groups.file || '',
				line: Number(match.groups.line),
				char: Number(match.groups.char),
			})
		}
	}

	return locations
}

/**
 * If a location is not found, this is the result that is used.
 */
const failureLocation: Location = {
	line: -1,
	char: -1,
	method: '',
	file: '',
}

/**
 * From a list of locations, get the location that is determined by the offset.
 * If none are found, return the failure location
 */
export function getLocationWithOffset(
	locations: Array<Location>,
	offset: Offset
): Location {
	// Continue
	let found: boolean = !offset.file && !offset.method

	// use while loop so we can skip ahead
	let i = 0
	while (i < locations.length) {
		const location = locations[i]

		// the current location matches the offset
		if (
			(offset.file &&
				(typeof offset.file === 'string'
					? location.file.includes(offset.file)
					: offset.file.test(location.file))) ||
			(offset.method &&
				(typeof offset.method === 'string'
					? location.method.includes(offset.method)
					: offset.method.test(location.method)))
		) {
			// we are found, and we should exit immediatelyg, so return with the frame offset applied
			if (offset.immediate) {
				// apply frame offset
				i += offset.frames || 0
				// and return the result
				return locations[i]
			}
			// otherwise, continue until the found condition has exited
			else {
				found = true
				++i
				continue
			}
		}
		// has been found, and the found condition has exited, so return with the frame offset applied
		else if (found) {
			// apply frame offset
			i += offset.frames || 0
			// and return the result
			return locations[i]
		}
		// nothing has been found yet, so continue until we find the offset
		else {
			++i
			continue
		}
	}

	// return failure
	return failureLocation
}

/**
 * Get each error stack frame's location information.
 */
export function getLocationsFromError(error: Error): Array<Location> {
	const frames = getFramesFromError(error)
	return getLocationsFromFrames(frames)
}

/**
 * Get the file path that appears in the stack of the passed error.
 * If no offset is provided, then the first location that has a file path will be used.
 */
export function getFileFromError(
	error: Error,
	offset: Offset = {
		file: /./,
		immediate: true,
	}
): string {
	const locations = getLocationsFromError(error)
	return getLocationWithOffset(locations, offset).file
}

/**
 * Get first determined location information that appears in the stack of the error.
 * If no offset is provided, then the offset used will determine the first location information.
 */
export function getLocationFromError(
	error: Error,
	offset: Offset = {
		immediate: true,
	}
): Location {
	const locations = getLocationsFromError(error)
	return getLocationWithOffset(locations, offset)
}

/**
 * Get the location information about the line that called this method.
 * If no offset is provided, then continue until the caller of the `getCurrentLine` is found.
 * @example Input
 * ``` javascript
 * console.log(getCurrentLine())
 * ```
 * @example Result
 * ``` json
 * {
 * 	"line": "1",
 * 	"char": "12",
 * 	"method": "Object.<anonymous>",
 * 	"file": "/Users/balupton/some-project/calling-file.js"
 * }
 * ```
 */
export default function getCurrentLine(
	offset: Offset = {
		method: 'getCurrentLine',
		frames: 0,
		immediate: false,
	}
): Location {
	return getLocationFromError(new Error(), offset)
}